Ag/Ce_1‐xMn_xO₂ Catalysts for Soot Oxidation in the Presence of NO_x and NO_x─CO: Role of Ce/Mn Molar Ratio

Abstract This study investigates the effectiveness in soot oxidation under tight and loose contact of Ag/CeO 2 , Ag/MnO x , and Ag/CeMnO x catalysts with different Ce:Mn molar ratios prepared by the citrate sol‐gel method. The sol‐gel method promoted the formation of a nanodomain structure in the CeMnO x composite. The interaction between cerium and manganese oxides and the Ce/Mn ratio were the key factors to form such a nanodomain structure. A 1:1 Ce/Mn ratio provided high activity and stability by preventing CeO 2 nanoparticle sintering, while at different Ce/Mn ratios deactivation eventually occurred. The presence of NO in the reaction mixture inhibited soot oxidation, while the CO presence in the NO + O 2 mixture limited such effect. The most promising Ag/CeMnO x catalyst with 1:1 Ce/Mn ratio was successfully applied to a cordierite monolith. Both powder and the monolithic catalysts selectively oxidized soot to CO 2 below 500 and 600 °C, respectively, demonstrating to be promising for practical applications in efficient soot oxidation.